1. Technical Field
The present invention relates to a digital communications signal processing apparatus applied to digital radar signal processing and a method therefor, and more particularly, to a digital signal processing apparatus in which windowing, Doppler filtering, and half phase filtering algorithms are successively performed, and a method therefor.
2. Related Art
The reason for using the windowing algorithm in digital signal processing and radar applications are to suppress Gibbs phenomenon generated due to discontinuity of signal data and to suppress generation of clutter signals.
One basic approach to designing a finite impulse response (FIR) digital filter is to first identify the infinite-duration impulse response by expanding the frequency response of an ideal filter in a Fourier series, and then to truncate and smooth this response using a window function. The most basic window is the rectangular window, where W.sub.r (n) can be shown as follows. W.sub.r (n)=1 when n&gt;=-M and n&lt;=m, and where W.sub.r (n)=0 otherwise. The use of the rectangular window corresponds to a direct truncation of the infinite-duration impulse response and leads to a solution exhibiting large ripples before and after the discontinuity of the ideal frequency response. This is the well-known Gibbs phenomenon.
The Gibbs phenomenon can be explained by the fact that H(.omega.) is related to the ideal response H.sub.id (.omega.)) and the frequency response of the window function ##EQU1##
through ##EQU2##
For the rectangular window, ##EQU3##
I have found that a load applied for calculation can be severe. I have also found that real-time processing of windowing, Doppler filter, and half phase filter algorithms cannot be implemented.